Manufactures of electrical devices such as computers continue to strive to make these devices more efficient. One way to make these devices more efficient is to lower the operating voltage of the device. Hence many of these devices utilize low voltage processors. Many low voltage processors can operate with a supply voltage of less than one volt. Such low voltage operation allows a device such as a computer to save significant power and run on battery power for extended periods of time. Further, with the advent of multi-core processors, power conservation has become more important for devices such as laptop computers. New manufacturing technologies such as technologies that can manufacture integrated circuit components that are smaller than 65-nm have created many additional technological challenges for designers of low voltage systems. One such challenge is related to higher intrinsic device variations (i.e. device leakage (Le) and threshold voltages (Vt)) associated with sub 65-nm manufacturing technology. Sensitivity of circuit parameters such as device switching at such low voltages due to manufacturing defects in another challenge for designers.
Generally, the minimum operating voltage (Vcc min) of a processor is limited by a minimum voltage that is required by memory systems in order to read from and write to memory cells. It can be appreciated that the amount of high performance data storage (i.e. memory cells) being incorporated with processors is ever increasing. Low voltage sub 65-nm processors that have low voltage, high performance memory typically have a significant yield loss during the testing and burn in procedure. These lower yields have made manufacturers of processors reconsider if lower voltages are economically feasible and what voltage levels are economically practical. Hence, there has been a trend to design and operate current processors at higher voltages than previous processors in an effort to provide an improved cost/performance trade off because of high performance memory problems. It can be appreciated that manufacturers are investing alternate circuit topologies to the conventional memory structures that can operate at lower voltages and can be manufactured with higher yields.